1,5-Anhydroglucitol (hereinafter, referred to as “1,5-AG”) is a reduced form of glucose where the C1 position is reduced, and a small amount of 1,5-AG is present in the living body. It was discovered that 1,5-AG is a useful control marker for diabetes (for example, see Non-patent Document 1 or 2).
As described in Non-patent Document 1,1,5-AG may be a marker ranked somewhere between the blood glucose level and hemoglobin A1c (HbA1c). Therefore, it is considered that the 1,5-AG level in blood could be a suitable marker for mild diabetic patients in their self-management of the disease.
TABLE 1MarkerCharacteristicsBloodMay erratically fluctuate up and down for a short time.glucose level1,5-AGIndicates the blood glucose level from about five toseven days before the test.HbA1cIndicates the mean glucose level from about two monthsbefore the test.
As disclosed in Non-patent Document 2, the 1,5-AG level in normal healthy people indicates a monosaccharide component that is the second most abundant in the blood after glucose. According to a clinical investigation conducted on a Japanese population, the average level of 1,5-AG is 24.6±7.2 (mean±SD) μg/ml. The physiologically-fluctuating range among individuals is small, and the 1,5-AG level is hardly influenced by fluctuation during the course of a day or over several days. In general, a male tends to have a level of 1,5-AG slightly higher than a female. The cutoff value is about 14.0 μg/ml, where 95% of healthy people are diagnosed as “normal”.
As a method of determining 1,5-AG, a gas chromatography method or an enzymatic method has been conventionally used, as described in Non-patent document 1. In the enzymatic method, 0.2 ml of a test sample of blood plasma (blood serum) is subjected to a protein removal treatment, and then, the content thereof is subjected to a mini-column to further remove contaminants included therein. Subsequently, the sample is treated with a pyranose oxidase (hereinafter, referred to as “PROD”). Then, hydrogen peroxide produced by the oxidation reaction of the hydroxyl group at the C2 position of 1,5-AG is stained by use of horseradish peroxidase (HRP), and the absorbance is measured at 420 nm Such a technique can be mentioned as an example of the enzymatic method. A determination kit specific to blood samples using such an enzymatic method has been developed.
Non-patent Document 1: Atsuo KAWAI and Yasuo AKANUMA, “1,5-anhydroglucitol”, “Rinsyo-Kensa”, vol. 33, No. 8, 1989 August, pp. 901-907.
Non-patent Document 2: “Medical Technology” (an extra edition), 2002, Vol. 30, No. 13, “All about diabetes testing—Screening to Testing for Complication”, pp. 1498-1499 (Ishiyaku Pub, Inc.).